In recent years, in the information and telecommunications field, maintenance of communication traffic using optical signals has been progressed rapidly, and so far backbone-, metro-, and access-system fiber-optic networks for relatively long distance communication of several kilometers or more have been deployed. From now on, furthermore, it is effective to use optical signals for processing a large amount of data without delays in short distance rack-to-rack (several meters to several hundred meters) and intra-rack (several centimeters to several ten centimeters) communications, and use of light in inter-LSI transmission and LSI-to-backplane transmission inside information equipment such as a router and a server is being advanced. In optical wiring between equipment/inside equipment, for example in a rack such as a router/switch, high-frequency signals transmitted from the outside by the Ethernet and the like through an optical fiber are input to a line card. Several line cards are used for one backplane, signals input to each line card are further gathered at a switch card through the backplane, and after processing the signals in an LSI in the switch card, the signals are output again to each line card through the backplane. Here, in an existing device, currently signals of several hundred Gbps or more from each line card are gathered at the switch card through the backplane. To transmit the signals with existing electrical wirings, it is necessary to divide the signals to approximately several Gbps per wiring because of propagation loss, and thus 100 or more wirings are necessary.
Furthermore, a pre-emphasis/equalizer for the high-frequency lines, and countermeasures for reflection or crosstalk between wirings are necessary. When systems handle further larger capacities from now on, and a device processes information of Tbps or more, problems such as the number of wirings and countermeasures for crosstalk become more serious with conventional electrical wirings. In contrast, use of light in signal transmission lines between intra-rack boards of a line card, a backplane, and a switch card, and furthermore intra-board chips is promising because it allows propagation of high-frequency signals of 10 Gbps or more with low loss so that the number of wirings is allowed to be less, and the above-described countermeasures become unnecessary even for high-frequency signals.
To realize such a high-speed optical interconnection circuit and apply in equipment, an optical wiring board using, for signal wiring, an optical waveguide that excels in performance and parts mountability with an inexpensive fabrication means is necessary. As an example of an optical wiring board using an optical waveguide, an example of an optical waveguide board in which an optical waveguide layer and a beam turning mirror member are formed integrally is disclosed in Patent Literature 1. In this example, an optical-electrical wiring board has aboard having an electrical wiring, an optical wiring layer having a core and a clad positioned on at least one surface of the board, and a mirror member embedded between the board and the optical wiring layer. Also, the board is fabricated by using a manufacturing method including a step of arranging the mirror member on the board, and a step of forming the optical wiring layer to cover the mirror member on the board. In this way, by arranging the mirror member on the optical wiring board, and forming the optical wiring layer to cover the mirror member, the mirror member can be arranged at an arbitrary position on the board, and flexibility of mounting layout improves. Also, by fabricating the mirror member separately, and placing the mirror member on the board, aggravation of a board fabrication yield ratio accompanying the mirror fabrication step can be avoided.
Also, as another example of conventional techniques of a method of manufacturing an optical waveguide board, Patent Literature 2 discloses an example of a method of manufacturing a mirror for deflection to an optical waveguide. In this example, in the method of manufacturing a mirror for deflection to an optical waveguide, in forming the deflection mirror in the optical waveguide by making a cut in the optical waveguide to form a groove having a slope surface with a dicing blade at least one surface of which has a desired slope angle, one having a planar part with width same as or larger than the depth of the groove at a tip surface of a cutting edge is used as the dicing blade. With the method of this example, a tapered surface of the deflection mirror and an end surface of a wiring core can be formed with a single process of dicing; therefore, fabrication of an optical waveguide board retaining a deflection mirror is possible with fewer fabrication steps.